反应烧结制备AION-AIN复相陶瓷及其性能

以AlN和Al2O3为原料、Y2O3为烧结助剂,在氮气气氛下无压反应烧结制备了AlON-AlN复相陶瓷;用XRD及SEM等方法对复相陶瓷的物相组成和显微结构进行了表征;研究了烧结温度、Al2O3及Y2O3加入量对复相陶瓷的烧结性能、力学性能和热导率的影响.结果表明:在1 650～1 800℃范围内反应烧结可以得到AjON-AlN复相陶瓷;其抗弯强度和热导率均随着烧结温度的升高先增大后减小,分别在1 750℃与1 700℃时达到最大值(378MPa,38 W·m-1·K-1);随着Al2O3加入量的增加,复相陶瓷的抗弯强度先增大后减小,当Al2O3加入量为30%时达到最大值,其热导率则随着Al2O3加入量的增加呈明显下降趋势;随着Y2O3加入量的增加,抗弯强度不断增大,而热导率则先增大后减小,在Y2O3加入量为3%时达到最大值41 W·m-1·K-1.     

SiC含量和热压烧结温度对AlN-SiC复相陶瓷材料导热性能的影响

采用热压烧结工艺制备了AlN-SiC复相陶瓷材料,用XRD、SEM和激光导热仪等研究了SiC加入量和烧结温度对复相陶瓷材料导热性能的影响.结果表明:当质量分数在20%～75%范围内,随着SiC含量的增加,复相陶瓷材料的热导率逐渐增大,最大热导率达到了88.92 W·m-1·K-1;进一步增加SiC的含量,复相材料的热导率又呈现下降趋势,当SiC质量分数为80%时,热导率降到了42.70 W·m-1·K-1;当SiC质量分数为20%时,随着烧结温度的升高(1 800～1 950℃),复相陶瓷材料的热导率逐渐上升,从42.15 W·m-1·K-1增加到68.41 W·m-1·K-1.     

烧结助剂La2O3含量对热压烧结制备Si3N4-AlN复相陶瓷性能的影响

以Si3N4和AlN为原料,La2O3为烧结助剂,在氮气气氛和1 800℃、30 MPa压力下热压烧结保温1 h制备出了Si3N4-AlN复相陶瓷,研究了La2O3含量对复相陶瓷烧结性能、抗弯强度、热导率及介电损耗的影响.结果表明:随La2O3含量的增加,复相陶瓷的孔隙率先减小然后趋于稳定,Si3N4由α相向β相逐渐转...     

两面顶技术低温超高压烧结AlN陶瓷的研究

研究了掺杂不同质量分数的Y2 O3的AlN陶瓷在超高压状态下烧结的第二相组成和微观结构。研究表明 ,Y2 O3是有效的低温烧结助剂 ,在低温超高压烧结下 ,掺杂不同比例烧结助剂的AlN陶瓷的第二相均为Al5Y3O12 ,在 4 .4× 10 3MPa ,15 0 0℃ ,1h的实验条件下 ,超高压烧结AlN陶瓷有着较好的微观结构 ,热导率可达到 130W /(m·K)。     

MgO-Y2O3烧结助剂对光固化成形Si3N4陶瓷显微结构及性能的影响

采用MgO-Y₂O₃作为烧结助剂，利用光固化成形技术、结合气压烧结方法制备了高致密化程度和高性能的Si₃N₄陶瓷。研究了Mg O-Y₂O₃烧结助剂总掺量对光固化成形Si₃N₄陶瓷的相对密度、物相组成、显微结构、热学和力学性能的影响。研究结果表明，随着Mg O-Y₂O₃烧结助剂总掺量的增加，光固化成形Si₃N₄陶瓷的相对密度和平均晶粒尺寸逐渐增大，总掺量为10wt%时，达到最大值，分别为99.01%和0.82μm；而热导率和抗弯强度均呈先增大后降低的变化趋势，并在8wt%达到最大值，分别为59.58 W·m^-1·K^-1和915.54 MPa。     

利用废料直接烧结制备CaO-Al2O3-SiO2微晶玻璃及其性能

以废玻璃、粉煤灰和氧化钙为原料,采用直接烧结法制备了CaO-Al2O3-SiO2(CAS)微晶玻璃;研究了CaO加入量和烧结温度对微晶玻璃烧结性能、晶相组成、显微结构和抗弯强度的影响。结果表明:随着CaO加入量的增多以及烧结温度的升高,微晶玻璃的体积密度先增大后减小;高的CaO加入量和烧结温度促进了柱状硅灰石晶相的生成;CAS微晶玻璃抗弯强度与体积密度的变化趋势基本相同;加入CaO质量分数为18%、在1 100℃烧结2h制备的CAS微晶玻璃的体积密度最大,为2.26g.cm-3,其主晶相为单一β-硅灰石,结晶度为50.7%,抗弯强度最大,为81.5MPa。     

烧结温度对Al_2O_3/SiC(n)纳米复相陶瓷性能的影响

采用极性分散剂 ,在微米Al2 O3 基体中加入SiC纳米颗粒 ,用真空热压烧结法制备出Al2 O3 /SiC(n)纳米复相陶瓷 ;研究了烧结温度对氧化铝纳米复相陶瓷性能的影响。研究结果表明 :烧结温度的不同使得烧结后Al2 O3 /SiC(n)纳米复相陶瓷的所得相和力学性能都有较大差异     

Na_2O含量对金刚石砂轮用Na_2O-SiO_2-Al_2O_3-B_2O_3系陶瓷结合剂性能的影响

采用球磨法制备Na_2O质量分数分别为12.31%,9.31%,7.31%的Na_2O-SiO_2-Al_2O_3-B_2O_3系陶瓷结合剂,研究了Na_2O含量对烧结前后陶瓷结合剂的物相组成、力学性能、热膨胀系数,以及对陶瓷结合金刚石砂轮抗弯强度的影响。结果表明:较高的Na_2O含量有利于抑制石英相的析出;随着Na_2O含量的增加,烧结后陶瓷结合剂的硬度和抗弯强度降低,热膨胀系数在较低温度(620~640℃)烧结后增大,在较高温度(660~680℃)烧结后先增后降;当Na_2O的质量分数为9.31%、烧结温度为680℃时,所得陶瓷结合金刚石砂轮的抗弯强度最大,为53.5 MPa;3种陶瓷结合剂制备得到的金刚石砂轮具有相似的微观结构。     

烧结工艺和碳加入量对Mo_2FeB_2基金属陶瓷显微组织和力学性能的影响

采用反应烧结法制备了Mo2FeB2基金属陶瓷,用扫描电镜、能谱仪及X射线衍射仪等手段研究了烧结工艺和碳加入量对其显微组织和力学性能的影响.结果表明:随着碳加入量的增大,金属陶瓷的硬度和抗弯强度均先增大再减小;当添加0.5%的碳时,在1 100℃保温60 min并最终在1 280℃烧结60 min,能够获得完全致密且力学性能较好的MozFeB2基金属陶瓷,其抗弯强度达到1 176 MPa.     

Y_2O_3掺杂对CaTiO_3陶瓷烧结性能和微观结构的影响

以CaO和TiO2为原料,外加质量分数分别为0,1%,2%,3%,4%的Y_2O_3后,分别在1 300,1 400℃保温3h烧结制备CaTiO_3陶瓷,研究Y_2O_3掺杂量和烧结温度对陶瓷物相组成、晶体结构、烧结性能和微观结构的影响.结果表明:随着Y_2O_3掺杂量的增加,CaTiO_3的晶胞体积先增大后减小,Y~(3+)置换Ti~(4+)使CaTiO_3晶胞体积增大,置换Ca~(2+)则使晶胞体积减小;随Y_2O_3掺杂量的增加或烧结温度的升高,陶瓷的烧结线收缩率和体积密度均增大;随Y_2O_3掺杂量的增大,陶瓷的显微结构更为致密,CaTiO_3晶粒尺寸先增大后减小,晶粒形状由不规则台阶状转变为规则形状.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.